Prior ammonia digestion processes to produce ammonium molybdate from molybdenum trioxide involve the use of open vessels which allow ammonia to escape to the air. As a result, large amounts of ammonia are needed to accomplish the conversion to ammonium molybdate. For example, it is typical to use in excess of 3 times the stoichiometric amount needed to produce ammonium molybdate. This adds significantly to the cost of the process.
According to the present invention, sealed tanks are used for the digestion, and the amount of ammonia that is used is significantly reduced. Furthermore, the recovery of molybdenum is essentially 100% efficient.